Mandalorian Armor was invented a few years after the blaster was invented. Because those shots hurt....kind of. Since retreating and/or surrendering was not an option in Mandalorian culture, the
brute noble warrior race decided to slap on some duracrete plates on their chests, a pair of tin cans on their wrists and a latrine bucket on their heads.
When the Jedi got pissed at the Mandalorians, they attacked them. One Jedi tried to cut a Mandalorian in half, but his armor saved him. Since the Jedi didn't known how to fight with anything but weakling lightsabers, all the Jedi shat themselves at once.